System to test thermal oxidizer efficiency

ABSTRACT

An apparatus (9) for testing the efficiency of a thermal oxidizer (200) is described. The apparatus provides for a test chemical to be directed into a thermal oxidizer so that the entry and exit flow rates of test chemical through the termal oxidizer may be accurately measured. In a portable version, the apparatus is formed of a platform (10), a tank (26) for holding liquid test chemical to test chemical vapor, and a device (94) to measure the flow rate that liquid test chemical enters the vaporizer from the tank. Methodology employing the apparatus, which provides numerical data useful in determining the efficiency of a thermal oxidizer, is described.

FIELD OF THE INVENTION

The present invention relates to an apparatus useful for determining theefficiency of a thermal oxidizer, as well as a method for using theapparatus.

BACKGROUND OF THE INVENTION

In many manufacturing settings there is a need to dispose of waste gasstreams. While the simplest and least expensive disposal method is toexhaust the gas stream into the ambient atmosphere, such a disposalmethod may cause harm to the environment, and may violate federal, stateor local pollution control laws in those instances where the waste gasstream contains organic chemicals. It has therefore become commonpractice to pass waste gas streams through a scrubber, in order toremove certain organic components from the gas stream and allow the gasstream to be safely exhausted into the atmosphere.

One device commonly used for removal of organic chemicals from a wastegas stream is a thermal oxidizer. In a typical thermal oxidizer, thewaste gas stream is combined with an oxygen-containing gas stream, e.g.,air, and then passed through a flame produced by burning a combustiblesubstance, e.g., natural gas. This process oxidizes the organicchemicals and converts them into carbon dioxide and water. The thermaloxidizer thus converts certain organic chemicals into environmentallyharmless chemicals that may be safely exhausted into the atmosphere. Inmany modern manufacturing plants, thermal oxidizers are permanentlyinstalled in gas exhaust ducts.

While in theory and preferred practice, a thermal oxidizer can oxidizeall or substantially all of the undesirable organic chemicals in a wastegas stream, in actual practice the thermal oxidizer may not be workingas expected or desired. For example, the incoming waste gas stream maybe flowing too quickly to allow complete oxidation of all the componentorganic chemicals, or there may be inadequate contact between the wastegas stream and the flame. It is therefore desirable, and often requiredunder pollution control laws, to periodically test the efficiency of athermal oxidizer.

To calculate the efficiency of a thermal oxidizer, one needs todetermine the extent to which incoming organic chemicals are oxidized tocarbon dioxide and water. Thus, one needs to know the mass flow rate ofthe organic chemicals entering the thermal oxidizer. Commonly, andaccording to procedures set forth by the United States EnvironmentalProtection Agency (EPA), a test chemical is introduced into a waste gasstream at a point prior to the waste gas stream being subjected tooxidization in the thermal oxidizer, i.e., upstream of the thermaloxidizer. The test chemical should be introduced to the gas stream at aknown and controllable mass flow rate, which is assumed to be the massflow rate at which the test chemical enters the thermal oxidizer.

When the test chemical is a gas, one can reasonably assume that themeasured rate at which the test chemical enters the gas stream, on theinlet side of a thermal oxidizer, is equal to the actual rate at whichthe test chemical enters the thermal oxidizer. However, when the testchemical is a liquid, the same assumption may not hold true. Forexample, according to the prior art, a liquid test chemical may beinjected into the inlet waste gas stream by way of an atomizer placedinside the duct that directs a waste gas stream into the thermaloxidizer. This is known as the aspirator technique of introducing liquidtest chemical into a waste gas stream. While it is easy to monitor therate at which the liquid test chemical is sent through the atomizer, onemay find, after the efficiency test is completed, that the duct(s)between the atomizer and the thermal oxidizer is covered by droplets, ifnot pools, of the liquid test chemical. In this situation, one cannotuse the measured rate that liquid test chemical is sent into the duct asa basis for determining the efficiency of the oxidizer, because thatmeasured rate is clearly not equal to, and has no known correlationwith, the rate that test chemical actually enters the oxidizer.

Based on the foregoing, it can be seen that there is a pressing need inthe art for an apparatus and method for reliably introducing a known andcontrolled rate of liquid test chemical into a thermal oxidizer, so thatthe efficiency of the thermal oxidizer can be accurately determined.

SUMMARY OF THE INVENTION

Briefly stated, one aspect of the present invention is an apparatus fortesting the efficiency of a thermal oxidizer. The apparatus comprises(a) a tank containing at least one liquid test chemical; (b) avaporizer, in fluid communication with the tank, for vaporizing the atleast one liquid test chemical to form test chemical vapor; (c) athermal oxidizer for oxidizing organic components in a gas stream; (d) aduct in fluid communication with the thermal oxidizer for directing awaste gas stream into an inlet side of the thermal oxidizer, the ductalso being in fluid communication with the vaporizer to allow the testchemical vapor and the waste gas stream to form a first mixture in theduct, the mixture entering an inlet side of the thermal oxidizer andexiting an outlet side of the thermal oxidizer having been convertedthereby to a clean gas stream; (e) means for measuring a flow rate ofthe at least one liquid test chemical entering the vaporizer from thetank; and (f) means for measuring a flow rate of the test chemical vaporor oxidation product thereof exiting the thermal oxidizer.

According to another aspect of the invention, a portable apparatususeful in measuring the efficiency of a thermal oxidizer is provided.The portable apparatus comprises (a) a platform having either directlyor indirectly mounted thereto (i) a tank holding at least one liquidtest chemical (ii) a vaporizer, in fluid communication with the tank,for vaporizing the at least one liquid test chemical received from thetank to form test chemical vapor, and (b) means for measuring a flowrate of the at least one liquid test chemical entering the vaporizerfrom the tank.

The invention also provides a method for determining the efficiency of athermal oxidizer. The method comprises the steps of (a) introducing atleast one liquid test chemical into a vaporizer at a measured flow rateover a period of time; (b) vaporizing the test chemical to form testchemical vapor; (c) directing the test chemical vapor into an entry ductof a thermal oxidizer, the duct containing a gas stream which iscombined with the test chemical vapor to form a first mixture; (d)directing the first mixture through the entry duct and into an inletside of the thermal oxidizer; (e) measuring a flow rate of the testchemical vapor or a oxidation product thereof exiting an outlet side ofthe thermal oxidizer; and (f) calculating the efficiency based on theflow rates of steps (a) and (e).

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe preferred embodiment of the invention, will be better understoodwhen read in conjunction with the appended drawings. For the purpose ofillustrating the invention, there is shown in the drawings an embodimentwhich is presently preferred. It should be understood, however, that theinvention is not limited to the precise arrangements andinstrumentalities shown.

Like numerals are used to indicate like elements throughout thedrawings. In the drawings:

FIG. 1 is a schematic representation of an efficiency tester accordingto the present invention mounted on a skid according to the invention;and

FIG. 2 is an enlarged cross-sectional view of an injection nozzle of theefficiency tester of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenienceonly and is not limiting. The words "above" and "below" designatedirections in the drawings to which reference is made. The words"upstream" and "downstream" refer to the direction of the flow of a gasin a passageway, i.e., gas flows from the "upstream" end of a pipetoward the "downstream" end of a pipe. The terminology includes thewords above specifically mentioned, derivatives thereof, and words ofsimilar import.

The invention is directed to an apparatus and method useful indetermining the efficiency of a thermal oxidizer. A preferred apparatusof the invention, and its operation to test the efficiency of a thermaloxidizer, will now be explained with reference to FIGS. 1 and 2. Theapparatus 9 of FIGS. 1 and 2 may be utilized in the United States EPAtest Method Nos. 18, 26A and 7D for determining the efficiency of athermal oxidizer. The disclosures of these EPA test Methods are hereinincorporated by reference, in their entirety.

FIG. 1 shows a platform in the form of a skid 10, to which the othercomponents of the apparatus are directly or indirectly connected. Apreferred skid 10 has a length 14 of about 6 feet, a width 18 of about 6feet, and a height 22 of about 1 foot. The skid 10 preferably containsslots of approximately 8 inch (20 cm) cross-section (not shown) toreceive the arms of a forklift, so that the skid 10 can be transported.As the apparatus of the invention typically weighs several hundredpounds, the skid 10 is preferably constructed of a sturdy material, suchas, for example, aluminum plate of 1/4 inch thickness. Such a skid maybe constructed by Innofab Corp. of Norristown, Pa.

It will be understood by one skilled in the art, based on thisdisclosure, that if portability is not a desired or necessary feature ofthe apparatus 9, then the following components could be mounted toconcrete or any other solid foundation, to thereby permanently locatethe apparatus near a thermal oxidizer. However, an advantage of mountingthe below-described components of the apparatus 9 to a skid 10 is thatthe apparatus 9 is then portable, and can be moved between thermaloxidizers. Because it is not necessary to constantly monitor theefficiency of a thermal oxidizer, a portable testing apparatus 9according to the invention offers the advantage that it can be relocatedto various thermal oxidizers when compliance testing is desired, thusmaking efficient use of the efficiency tester.

Connected to the skid 10 or other suitable base is a holding tank 26,preferably having an appended sight gauge 30 as shown. Liquid testchemical (not shown) is stored in the tank 26, prior to entering avaporizer 86. The capacity of the holding tank 26 will depend on theamount of test chemical desirably sent through the vaporizer. Forexample, a 240 gallon (910 liter) holding tank is satisfactory for usewhen the test chemical is toluene, while a 135 gallon (510 liter)holding tank is satisfactory when the test chemical is methylenechloride. A preferred holding tank 26 is ASME code pressure rated to apressure of about 125 psig, and is available from John Wood Co. (Oaks,Pa).

The sight gauge 30 allows the operator to easily see approximately howmuch test chemical is in the holding tank 26. Such a sight gauge 30suitable for use in the apparatus 9 is available from A. T. Chadwick(Bensalem, Pa).

Built into the holding tank 26 is a filling port 34, through whichliquid test chemical may be added to the holding tank 26, and a drainport 38, which allows liquid test chemical to be drained from the tank26. If the apparatus 9 is portable, the holding tank 26 is preferablydrained prior to the apparatus 9 being transported to another site foran efficiency measurement. The drain port 38 is in fluid communicationwith a ball valve 42, for opening and closing the drain port 38.Likewise, the filling port 34 is in fluid communication with a series oftwo ball valves, 46, 50, which flank a pressure indicator 48 that isuseful to indicate the chemical fill line pressure. Test chemical may becharged to the holding tank 26 from bulk storage tanks (not shown),using pumps (not shown) and a suitable conduit (not shown) such as, forexample, 1/2 inch (1.24 cm) Hytron™ transfer hose. Suitable hosing isavailable from Airline Hydraulics (Bensalem, Pa).

As a thermal oxidizer's efficiency is stated in terms of theeffectiveness of the thermal oxidizer at removing a chemical(s) from awaste gas stream, the liquid test chemical used to evaluate theefficiency of the thermal oxidizer is preferably the same or similar tothe chemical to be removed. Thus, if the objective is to determine theefficiency of a thermal oxidizer at removing toluene, for example, froma waste gas stream, the preferred test chemical to be used in theapparatus 9 is toluene.

Preferred liquid test chemicals for use in the present invention includetoluene and methylene chloride. Toluene is preferred for determining theefficiency of a thermal oxidizer at removing hydrocarbons, andespecially aromatic hydrocarbons, from a waste gas stream. Methylenechloride, being a chlorinated hydrocarbon, is preferred for determiningthe efficiency of a thermal oxidizer at removing chlorinatedhydrocarbons from a waste gas stream. A liquid test chemical accordingto the invention may also be a mixture of liquid test chemicals, e.g., amixture of toluene and methylene chloride.

While toluene and methylene chloride are preferred liquid testchemicals, other suitable liquid test chemicals include, for example andwithout limitation, amyl alcohol, butyl acetate, butyl alcohol, chloral,cyclohexanone, decane, ethyl benzene, furfural alcohol, isoamyl alcohol,isoamyl acetate, isobutyl alcohol, isobutyl acetate, methyl isobutylketone, tetrahydrofuran and xylene.

According to the invention, the holding tank 26 is in fluidcommunication with vaporizer 86, and there is (1) a forcing means forforcing the liquid test chemical from the holding tank 26 into thevaporizer 86 in a continuous, controllable and rate-determinable manner,and (2) a controlling means for controlling the flow rate of the liquidtest chemical entering the vaporizer 86 from the holding tank 26.

In a preferred embodiment of the invention, the forcing means preferablyincludes a pressurized gas, such as from a cylinder, venturi valve,blower or similar apparatus for providing pressurized gas. Thepressurized gas is preferably from a cylinder of gas, preferablynitrogen gas from a cylinder at location 58 (gas cylinder not shown).When the efficiency tester is in operation, the pressured gas impingeson liquid test chemical situated in the holding tank 26. The pressurizedgas exerts force on the liquid test chemical, causing the chemical to beexpelled from the tank 26, run through piping 90, and enter thevaporizer 86. Thus, the pressurized gas is in fluid communication with,and upstream of, the liquid test chemical.

According to the preferred embodiment shown in FIG. 1, the holding tank26 includes a port 54 to provide for fluid communication between thetank 26 and a source of pressurized gas (not shown) at location 58 viapiping 78. The pressurized gas is preferably nitrogen but may also becompressed air, and preferably is capable of exerting at least about 35psig pressure on the test chemical. About 5 to about 10 psig pressure issufficient to provide a test chemical entry rate, into the vaporizer 86,of about 200 lb/hr (about 90 kg/hr) for methylene chloride, and about600 lb/hr (about 270 kg/hr) for toluene. Suitable vaporizer 86 entryflow rates for the liquid test chemical according to the presentinvention range from about 35 kg/hr to about 500 kg/hr, depending on thedesign of the vaporizer.

Forcing means other than pressurized gas may be employed according tothe invention, for forcing liquid test chemical into the vaporizer 86.For example, the tank 26 of liquid test chemical may be held at analtitude above the vaporizer 86, so that gravity can be exploited toprovide sufficient forcing energy. Another suitable forcing means is apump that is situated in the piping 90 that runs from the holding tank26 to the vaporizer 86. Based on this disclosure, one skilled in the artwill understand that other forcing means may be used in the presentinvention as long as the forcing means provides sufficient constantenergy to force test chemical from the tank 26 through piping 90 tovaporizer 86.

The controlling means preferably includes a valve, such as valve 70,preferably positioned between the holding tank 26 and the gas cylinder(not shown) at position 58, which allows the pressure exerted on theliquid test chemical to be controlled. The valve preferably serves asthe controlling means for controlling the flow rate of the liquid testchemical entering the vaporizer 86.

According to the preferred apparatus 9 shown in FIG. 1, valves 62, 66,70 and 74 are positioned in pipe 78. Valve 66 is a check valve, usedhelp prevent liquid test chemical from flowing backward and entering thesource of pressurized gas (not shown) located at position 58. Globevalve 70 is a pressure control valve, which can regulate the pressure ofgas exiting the cylinder (not shown) at position 58, to allow for asuitable and controllable pressure to be exerted against the liquid testchemical. Ball valves 62 and 74 are preferably present in order to allowcontrol valve 70 to be isolated for repair and adjustments as necessary.

Also connected to the holding tank 26, according to a preferredembodiment of the invention, is a pressure relief valve 76, that may beused to relieve any excess pressure that builds up in the holding tank26. The relief valve 76 preferably has a pressure rating of 40-45 psig.

Also built into the holding tank 26 is an exit port 82, which ispreferably in fluid communication with the vaporizer 86. Installedin-line with piping 90, where piping 90 connects the tank 26 to thevaporizer 86, is a means for measuring the flow rate at which liquidtest chemical enters the vaporizer 86. A preferred measuring means is aflowmeter 94 as shown in FIG. 1, positioned in-line with piping 90. Theflowmeter 94 measures the flow rate of the liquid test chemical inpiping 90 exiting the holding tank 26 and entering the vaporizer 86.

It should be understood from this discussion that any suitable flowmeterfor monitoring the flow rate of liquid test chemicals may be used withthe present invention. Preferably, a floating ball flowmeter, orrotameter, is used as the flowmeter in the present invention. Such aflowmeter is available as Model 1110 from Brooks Instruments (Ambler,Pa). Preferably, the flowmeter responds to changes in the temperature ofthe fluid passing through the meter, and has a design accuracy of ±2% ofthe calibrated flow rate. Thus, the flowmeter is preferably calibratedfor the specific test chemical being employed.

Suitable piping, such as piping 78 and 90, that may be used throughoutthe apparatus as shown in FIGS. 1 and 2, is Schedule 40 carbon steelhaving 1.5 inches (3.8 cm) fiberglass insulation. The pipe preferablyhas an inner diameter (ID) sufficient to allow about 70 lb/hr to about210 lb/hr of liquid test chemical to pass through the pipe. Preferablyin-line with piping 90 that leads from the exit port 82 to the flowmeter94 are two ball valves, 98 and 102 as well as a pressure indicator 104.Valve 98 allows for the chemical flow from tank 26 to be shut off in anemergency. Valve 102 is used to adjust and maintain a steady flow ofliquid test chemical into the flow meter 94. A drain valve 106 ispositioned in the piping 90 between the flowmeter 94 and the vaporizer86. The drain valve 106, when open, allows for liquid test chemical tobe drained from the piping 90. Another valve, 108, is preferably placedin-line with piping 90 at a site just before the piping 90 is connectedto the vaporizer 86. The valve 108 allows for quick shut off of the testchemical to the vaporizer 86, and eliminates the need to readjust valve102 during shut down and start up of the thermal oxidizer efficiencytest procedure.

The vaporizer 86 is capable of converting liquid test chemical, i.e., anorganic chemical in a liquid state that will be used to test theefficiency of the thermal oxidizer, to test chemical vapor, i.e.,vaporized liquid test chemical. It will be understood from thisdisclosure that any suitable vaporizer may be used in the presentinvention. Preferably, the vaporizer 86 contains an entry port forintroducing the liquid test chemical into the vaporizer, a chamberwherein the liquid test chemical is converted to test chemical vapor,and an exit port for the exit of test chemical vapor from the vaporizer.As shown in FIG. 1, the longitudinal axis of the vaporizer 86 ispreferably perpendicular to the plane in which the skid 10 or otherplatform lies. However, the longitudinal axis of the vaporizer may alsobe situated parallel to the plane in which the skid 10 or other platformlies.

As shown in FIG. 1, the vaporizer 86 contains a first entry port 110, influid communication with the holding tank 26, and a second entry port114, in fluid communication with a source of steam 118. The first entryport 110 allows for the introduction of liquid test chemical into thevaporizer. The base 122 of the vaporizer 86 is preferably connected tothe skid 10. More preferably, the vaporizer 86 is bolted or welded tothe skid 10. Proximate to the base 122 is a drain port 126, in fluidcommunication with valves 130 and 134, and steam trap 138. The valvesystem 130 and 134 is useful to provide a quick heat-up of thevaporizer. Thus, valve 134 may be closed, then valve 130 opened,condensate quickly blown through valve 130, and after quick heat-up hasbeen achieved, valve 130 is closed and valve 134 opened to the steamtrap for normal operation. The vaporizer 86 also contains an exit port142, through which a stream of test chemical vapor in combination withsteam, may exit.

A preferred vaporizer incorporates a sight gauge 146, which is a pieceof pipe preferably appended to the outside of the vaporizer 86, andparallel to the longitudinal axis of the vaporizer as shown in FIG. 1,much like a handle runs along the outside of a mug. Suitable sightgauges have a transparent region to allow an operator to see the levelof chemical liquid and/or vapor that is inside the vaporizer. The sightgauge preferably runs from a site just above the entry port 110 for theliquid test chemical, and extends to a site just below the exit port 142for the test chemical vapor. A sight gauge so situated allows anoperator to see what is happening along a substantial length of thevaporizer 86, particularly in the region of the vaporizer 86 where theliquid test chemical is converted to a stream of test chemical vapor.

As shown in FIG. 1, the sight gauge 146 is connected to the vaporizer 86through a lower valve 150 and an upper valve 154. The valve 150 ispreferably positioned longitudinally between the first and second entryports, 110 and 114, respectively. The upper valve 154 is preferablypositioned approximately opposite the exit port 142. The diameter of thesight gauge is not critical. However, in a preferred embodiment of theinvention, a diameter of about 1 inch (2.54 cm) is suitable for thesight gauge.

The second entry port 114 is in fluid communication with a source ofsteam 118 by way of piping 158. The piping 158 preferably has an innerdiameter of about 1.5 inches (3.8 cm), and is capable of carrying steamhaving a pressure of at least about 80 to about 110 psig (about 550 toabout 750 kPa). Valves 162 (hand valve), 166 (hand valve), 170 (pressurecontrol valve), and 174, are positioned in-line the piping 158, andserve to control the pressure and flow of steam between the source ofsteam 118 and the second entry port 114 of the vaporizer 86. A pressureindicator 176 is positioned in-line with the pipe 158, between thevalves 170 and 174. Preferably, the steam enters the vaporizer throughthe second entry port 114 at a pressure of about 15 to about 35 psi(about 100 to about 230 kPa) as regulated by valve 170. The preferredsteam pressure is determined by the liquid test chemical used and therate the liquid test chemical enters the vaporizer. Higher steampressures are preferred for liquid test chemicals that have high boilingpoints. Valve 156, which extends from the top of the vaporizer 86, is amanual air release vent valve.

A preferred vaporizer 86 according to the invention is configured forproviding contact between the liquid test chemical and steam from thesource 118 of pressurized steam. When the steam contacts the liquid testchemical, the liquid test chemical is converted to test chemical vapor,thus forming a mixture of steam and test chemical vapor within thevaporizer. While the preferred vaporizer of the invention employs steamas an energy source to convert test chemical from a liquid to a vaporstate, alternative energy sources may be employed, with appropriatechanges to the vaporizer 86. For example, the vaporizer 86 might employa heated coil (not shown) that extends through the vaporization chamber(not shown), so that liquid test chemical that comes into contact withthe coil will be heated and converted into vapor. Gas, oil and electric(resistance) heating may all be employed in a vaporizer useful in theinvention.

Materials useful in the construction of vaporizers are well known in theart, and any such materials are suitable for preparing a vaporizeraccording to the instant invention. Preferred construction materials arelargely or completely inert, i.e., substantially unreactive with, bothliquid test chemical and test chemical vapor, under the conditionsemployed within the vaporizer. Suitable materials include, for example,stainless steel, carbon steel, monel, nickel or other metals or metalalloys, polyvinylchloride or other plastics, glass, etc., as well ascomposites thereof.

Suitable vaporizers may be obtained from many suppliers. The ThomasRegister (1995 Edition), under the heading "vaporizers", lists variousmanufacturers, located throughout the United States, that can providesuitable vaporizers. The preferred vaporizers 86 of the invention arethose vaporizers capable of converting liquid organic solvents tosolvent vapor in a continuous fashion, i.e., the vaporizer 86 ispreferably a continuous vaporizer, where a continuous vaporizersimultaneously accepts an incoming stream of liquid test chemical andexpels a vapor stream of test chemical, so that the mass flow rate atwhich the test chemical enters the vaporizer is substantially equal tothe mass flow rate at which the test chemical leaves the vaporizer 86through the exit port 142.

A preferred vaporizer 86 according to the invention is available fromArmstrong Engineering Associates, Inc. (West Chester, Pa), as their "D "standard model vaporizer, and has the ability to vaporize about 700-840pounds/hour of toluene, entering the vaporizer as liquid at about 50°F., wherein the heating medium is saturated steam at up to about 75 psigand about 320° F., and wherein the leaving vapor has a temperature ofabout 250° F. Such a vaporizer has an outer diameter of about 8 inches(about 20 cm) and a length of about 86 inches (about 220 cm). Byincreasing the steam pressure, a maximum throughput of methylenechloride of about 840 lb/hr may be achieved.

The apparatus of the invention, as best shown in FIG. 2, has a pipe 182running from the exit port 142 of the vaporizer 86 and terminatingwithin the passageway 196 of a duct 178 that directs a waste gas streaminto a thermal oxidizer 200. The duct 178 has a wall 180 that definesthe passageway 196 through which the waste stream flows on its way tothe thermal oxidizer. The passageway 196 extends longitudinally throughthe duct, and has an upstream end and a downstream end, where the arrow186 in FIG. 2 points toward the downstream end, and where the downstreamend is defined as being closer to the thermal oxidizer than the upstreamend of the passageway 196. A pump or fan (not shown) is typicallypresent in the duct in order to draw waste gas stream through thethermal oxidizer.

The pipe 182 has a longitudinal axis 184, an exterior surface 192, afirst end 204 connected to the exit port 142 of the vaporizer and anopen second end 208 terminating within the passageway 196 of the duct178. The pipe 182 extends through the wall 180 of the duct 178 by way ofa flange 214 which may already be present as part of the duct 178 or mayneed to be added to allow the pipe 182 to extend through the wall 180.The pipe 182 preferably extends upward from the vaporizer 86 to the duct178. The pipe 182 preferably has a valve (not shown) positioned in lineof the pipe 182 near the vaporizer exit port 142, which may be openedprior to beginning an efficiency test in order to establish that noliquid is present in the pipe 182 prior to beginning the efficiencytest.

The open end 208 of the pipe 182 terminates in an open angled planar endface 212. Preferably, the planar end face 212 is oriented in such a waythat it is directed toward the downstream end of the passageway 196, asshown in FIG. 1. Preferably, the angled end face 212 forms an acuteangle θ of about 50 to about 75 degrees, and more preferably about 60degrees with respect to the longitudinal axis 184 of the pipe. Thepreferred angled end face according to the invention increases theturbulence of the gas flow in the duct, and thus provides a better mixpattern for entainment of the test chemical vapor in the waste gasstream.

A temperature gauge 188 or similar temperature monitoring device ispreferably placed so as to monitor the temperature of the vapor flowingin the pipe 182. The inner diameter of the pipe 182 may be about 2inches (about 5 cm) when methylene chloride is the test chemical, andabout 3 inches (about 7.6 cm) when toluene is the test chemical. Thediameter of the pipe will vary depending on the identity of the testchemical, due to differences in the density and vapor pressure of thevarious test chemicals. In general, the pipe diameter should be selectedin view of the identity of the test chemical, as well as the flow rateand pressure drop that is desired, which in turn will depend on the pumpor fan selected to optimize system design.

When the liquid test chemical enters the vaporizer 86, it contacts steamand thus forms a second mixture comprising test chemical vapor andsteam. The second mixture exits the vaporizer through port 142, travelsthrough pipe 182 and enters the duct 178 on the inlet side of a thermaloxidizer 200. The duct 178 carries a waste gas stream, and when thewaste gas stream contacts the second mixture, a first mixture isproduced comprising test chemical vapor, steam and the waste gas stream.The first mixture is then directed into the inlet side of a thermaloxidizer. Upon passing through the thermal oxidizer, the first mixtureis converted into a clean gas stream. Depending on the efficiency of thethermal oxidizer, the clean gas stream may contain residual testchemical vapor, and/or may contain the oxidation products formed fromthe test chemical vapor. Thus, if the thermal oxidizer is a flamethermal oxidizer, the reaction products are typically the combustionproducts of hydrocarbons, which will typically include water and carbondioxide. Hydrochloric acid may also be an oxidation product in instanceswhere the test chemical vapor and/or waste gas stream containschlorinated hydrocarbons.

Thermal oxidizers are well known pollution control devices, commonlyused to treat effluent gases contaminated with combustible impurities.They operate by taking impurity-laden gas to high temperatures, in thepresence of oxygen, to thereby cause the combustion of the impurity andproduce purified gas. Thermal oxidizers are often employed where theimpurity in the gas is organic, and thus readily susceptible tocombustion. Thus, during operation, the thermal oxidizers of theinvention have an inlet side (not shown), for receivingimpurity-containing gas, and an outlet side (not shown), for releasingthe treated gas. Any thermal oxidizer known in the art may be usedaccording to the invention, and a thermal oxidizer that passesimpurity-laden gas through a flame, known as a flame thermal oxidizer,is well-suited to the inventive method.

In one embodiment, the inventive apparatus 9 is portable and does notinclude a thermal oxidizer. This embodiment is advantageous in that itmay be separated from a thermal oxidizer. The portable apparatus 9 issufficiently small that it can be transported between thermal oxidizerswhen an efficiency test is necessary. Also, when the apparatus 9 isbeing transported, it need not include a forcing means for forcing theliquid test chemical into the vaporizer, such as is provided by thesource of pressurized gas (not shown) located at position 58. This isbecause the portable apparatus may be connected to a source ofpressurized gas, or other forcing means, which is available at the siteto which the portable apparatus is taken.

The apparatus 9 of the invention may be employed to test the efficiencyof thermal oxidizers according to EPA test procedures, and in particularas set forth in EPA Reference Methods 18, 26A and 7D. However, themethod of the invention is not limited to use in these particular testmethods.

According to a preferred method, prior to beginning an efficiencydetermination, the entire apparatus shown in FIG. 1 is purged withnitrogen. Then, after ensuring that the drain valves 42, 106, 130 and134 are closed, the holding tank 26 is filled with a liquid testchemical, e.g., toluene or methylene chloride. Nitrogen gas at apressure of about 5 to about 10 psig (about 35 to about 70 kPa) is thendelivered from source (not shown) located at position 58 through port54, thus driving liquid test chemical through port 82 and piping 90 andinto the vaporizer 86 by way of the first entry port 110. When tolueneis the test chemical, a flow rate of about 600 pounds/hour (about 270Kg/hr) has been satisfactorily employed, while a flow rate of about 200pounds/hour (about 90 Kg/hr) has been found satisfactory when methylenechloride is the test chemical. Sufficient test chemical is deliveredinto the vaporizer to fill the vaporizer about one half full of liquidtest chemical.

Steam from source 118 is then directed through the second entry port 114of the vaporizer 86, which causes heating and vaporization of the liquidtest chemical. A steam pressure of about 5 to about 25 psi (about 35 toabout 175 kPa) is suitable when the test chemical is methylene chloride,while a higher pressure of about 20 to about 40 psi (about 140 to about280 kPa) is suitable when the test chemical is toluene, due to thehigher boiling point of toluene. Gradually, the liquid test chemicallevel will go down, as seen through the sight gauge 146. Additional testchemical is slowly added to the vaporizer, so that the mass beingtransferred from the holding tank 26 is equal to the mass being expelledfrom the vaporizer 86 through the port 142. The equilibrium point maytake some trial and error to reach, with variation in test chemical flowrate and steam pressure being the main parameters that will needadjusting.

An LEL monitor may be used to assist in determining the proper flowrates and pressures to provide a steady state flow. An LEL monitor is asafety device that constantly monitors the process air stream andrecords/shows the concentration of the gases in the duct. For example,it is useful so that an operator can be appraised if the concentrationof any vapor in the gas stream is approaching the lower explosionconcentration limit of that vapor. Preferably, compliance testing shouldnot commence until after an equilibrium has been established.

The test chemical/steam-mixture (the second mixture) exits the vaporizerthrough exit port 142, travels through the piping 182, and enters theduct 178 through the end 208 of the pipe 182. The temperature of thematerial in the line 182, which leads to the duct 178, should bemonitored periodically, using the temperature gauge 188, to make certainthat the temperature within pipe 182 does not fall below the boilingpoint temperature of the test chemical, which is, for example, 106° F.(40° C.) for methylene chloride and 230° F. (110° C.) for toluene. Ifthe temperature in the pipe 182 falls below the lower limit, an unsteadyflow rate for the test chemical vapor will result. If the temperaturewithin the pipe 182 begins to get undesirably low, then the steampressure through the vaporizer can be increased. The end 208 of the pipe182 preferably terminates in about the middle of the passageway 196 ofthe duct 178, where the duct 178 carries a waste gas stream to a thermaloxidizer. Thus, if the duct 178 has a diameter of about 36 inches, thepipe 182 will extend about 18 inches into the duct.

After being admixed with steam and test chemical vapor, the waste gasstream becomes a first mixture. The first mixture enters the thermaloxidizer, and then exits as a clean gas stream, having been purged of atleast some orgainic impurities that were present in the waste gas streamand first mixture. The exiting gas may have a residual amount of testchemical vapor. The amount of test chemical vapor present in the firstmixture, and the amount of test chemical vapor or oxidation productthereof in the clean gas stream, are determined and the efficiency ofthe thermal oxidizer may then calculated.

Determination of the amount of test chemical vapor or oxidation productthereof in the clean gas stream requires application of a means (notshown) for measuring a flow rate of the test chemical vapor or oxidationproduct thereof exiting the thermal oxidizer. Thus, the apparatus 9 ofthe invention provides a means for measuring a flow rate of testchemical vapor or oxidation product thereof exiting the thermaloxidizer, where a suitable means is set forth in EPA Reference Methods18, 26A and 7D. However, the method of the invention is not limited touse in these particular means for measuring a flow rate of the testchemical vapor or oxidation product thereof exiting the thermaloxidizer.

In an actual operation, three 1-hour tests were conducted at 1,500° F.operating temperature. Direct gas chromatography, in accordance with 40CFR 60, Appendix A, Reference Manual 18 of the EPA was used to determinethe emissions of carbon tetrachloride, methylene chloride, toluene,methanol, isopropanol and ethyl acetate. In a representative test run,methylene chloride in the inlet gas stream (first mixture) was 190.6lb/hr, and methylene chloride in the stack gases (in the clean gasstream exiting the thermal oxidizer) was 0.79 lb/hr, indicating thatmethylene chloride was combusted at a rate of 189.81 lb/hr. As 85 gramsof methylene chloride are consumed through oxidation for every 73 gramsof hydrochloric acid produced, the amount of hydrochloric acid producedthrough this test run was 163.0 lb/hr. The measured amount ofhydrochloric acid in the clean gas stream was 0.44 lb/hr. Thus, the acidremoval efficiency is equal to [(163.0-0.44)/163.0]×100=99.7%.

The apparatus and test method of the invention provide a reliable way tointroduce a known mass flow rate of liquid test chemical into a thermaloxidizer, so that the efficiency of a thermal oxidizer may be accuratelydetermined. Heretofore, measurements of thermal oxidizer efficiencies,using liquid test chemicals, have been subject to undesirable error dueto uncertainty regarding the amount of test chemical that actuallyentered the thermal oxidizer.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

What is claimed is:
 1. An apparatus for testing the efficiency of athermal oxidizer comprising:(a) a tank containing at least one liquidtest chemical; (b) a vaporizer, in fluid communication with the tank,for vaporizing the at least one liquid test chemical to form testchemical vapor; (c) a thermal oxidizer for oxidizing organic componentsin a gas stream; (d) a duct in fluid communication with the thermaloxidizer for directing a waste gas stream into an inlet side of thethermal oxidizer, the duct also in fluid communication with thevaporizer to allow the test chemical vapor and the waste gas stream toform a first mixture in the duct, the first mixture entering an inletside of the thermal oxidizer, being converted within the thermaloxidizer to a clean gas stream, and then exiting an outlet side of thethermal oxidizer as the clean gas stream; (e) means for measuring a flowrate of the at least one liquid test chemical entering the vaporizerfrom the tank; and (f) means for measuring a flow rate of the testchemical vapor or oxidation product thereof exiting the thermaloxidizer.
 2. The apparatus of claim 1 further comprising forcing meansfor forcing the at least one liquid test chemical from the tank into thevaporizer, and controlling means for controlling the flow rate of the atleast one liquid test chemical entering the vaporizer.
 3. The apparatusof claim 2 wherein the forcing means comprises a pressurized gas influid communication with, and upstream of, the at least one liquid testchemical.
 4. The apparatus of claim 3 wherein the controlling means is avalve for modulating pressure of the pressurized gas.
 5. The apparatusof claim 1 wherein the liquid test chemical flow rate measuring means isa flow meter.
 6. The apparatus of claim 5 wherein the flow meter is arotameter.
 7. The apparatus of claim 1 wherein the at least one liquidtest chemical is selected from the group consisting of toluene andmethylene chloride.
 8. The apparatus of claim 1 wherein the thermaloxidizer is a flame thermal oxidizer.
 9. The apparatus of claim 1wherein the vaporizer is in fluid communication with a source ofpressurized steam, and the vaporizer is configured for providing contactbetween the at least one liquid test chemical and steam from the sourceof pressurized steam to form a second mixture comprising test chemicalvapor and steam within the vaporizer.
 10. The apparatus of claim 9wherein the duct has a wall defining a passageway extendinglongitudinally through the duct, the passageway has an upstream end anda downstream end where the downstream end is defined as being closer tothe thermal oxidizer than the upstream end, the vaporizer comprises anexit port for releasing the second mixture from the vaporizer, and theapparatus further comprises a pipe having a longitudinal axis, anexterior surface, a first end connected to the exit port of thevaporizer and an open second end extending through the wall andterminating within the passageway.
 11. The apparatus of claim 10 whereinthe open end of the pipe terminates in an open angled planar end faceoriented in such a way that the open angled planar end face is directedtoward the downstream end of the passageway.
 12. The apparatus of claim11 wherein the angled end face forms an acute angle of about 55 degreesto about 75 degrees with respect to the longitudinal axis of the pipe.13. A portable apparatus comprising(a) a platform, the platform havingdirectly or indirectly mounted thereto:(i) a tank holding at least oneliquid non-aqueous test chemical; (ii) a vaporizer, in fluidcommunication with the tank, for vaporizing the at least one non-aqueousliquid test chemical received from the tank to form test chemical vapor;and (b) means for measuring a flow rate of the at least one non-aqueousliquid test chemical entering the vaporizer from the tank.
 14. Theapparatus of claim 13 further comprising forcing means for forcing theat least one liquid test chemical from the tank into the vaporizer, andcontrolling means for controlling the flow rate of the at least oneliquid test chemical.
 15. The apparatus of claim 14 wherein the forcingmeans comprises a pressurized gas in fluid communication with theinterior space of the tank.
 16. The apparatus of claim 14 wherein themeans for controlling the flow rate of the at least one liquid testchemical is a valve for modulating pressure.
 17. The apparatus of claim14 wherein the flow rate controlling means is a flow meter.
 18. Theapparatus of claim 17 wherein the flow meter is a rotameter.
 19. Theapparatus of claim 13 wherein the vaporizer is configured for receivingsteam from a source of pressurized steam, and for providing contactbetween the at least one non-aqueous liquid test chemical and steam fromthe source of pressurized steam to from a mixture comprising testchemical vapor and steam within the vaporizer.
 20. The apparatus ofclaim 13 wherein the vaporizer further comprises an exit port forreleasing the test chemical vapor from the vaporizer, and the apparatusfurther comprises an entry duct appended to an inlet side of thermaloxidizer for providing fluid communication between the vaporizer and theentry duct, and a pipe having a longitudinal axis, a first end connectedto the exit port of the vaporizer and a second end terminating in anopen end face lying in a plane, the second end extending into apassageway of the entry duct.
 21. The apparatus of claim 20 wherein thelongitudinal axis of the pipe and the plane of the open end face of thepipe intersect at an acute angle.
 22. The apparatus of claim 21 whereinthe acute angle is about 50 degrees to about 75 degrees.
 23. A methodfor determining the efficiency of a thermal oxidizer, comprising thesteps of:(a) introducing at least one liquid test chemical into avaporizer at a measured flow rate over a period of time; (b) vaporizingthe test chemical to form test chemical vapor; (c) directing the testchemical vapor into an entry duct of a thermal oxidizer, the ductcontaining a waste gas stream which is combined with the test chemicalvapor to form a first mixture; (d) directing the first mixture throughthe entry duct and into an inlet side of the thermal oxidizer; (e)measuring a flow rate of the test chemical vapor or oxidation productthereof exiting an outlet side of the thermal oxidizer; (f) calculatingthe efficiency based on the flow rates of steps (a) and (e).
 24. Aportable apparatus comprising(a) a platform, the platform havingdirectly or indirectly mounted thereto:(i) a tank holding at least oneliquid test chemical; (ii) a vaporizer, in fluid communication with thetank, for vaporizing the at least one liquid test chemical received fromthe tank to form test chemical vapor; and (b) means for measuring a flowrate of the at least one liquid test chemical entering the vaporizerfrom the tank; wherein the liquid test chemicals are selected from thegroup consisting of toluene, methylene chloride, amyl alcohol, butylalcohol, chloral, cyclohexanone, decane, ethyl benzene, furfuralalcohol, isoamyl alcohol, isoamyl acetate, isobutyl alcohol, isobutylacetate, methyl isobutyl ketone, tetrahydrofuran and xylene.